Personal care products, such as infant diapers, sanitary napkins, adult incontinence garments, and the like are generally constructed from a number of different components and materials. Such articles typically have some portion, usually the backing layer, liner, barrier or baffle constructed of a liquid repellent film material. This repellent material is appropriately constructed to minimize or prevent the exudation of the absorbed liquid from the article and to obtain greater utilization of the absorbent capacity of the product. Liquid repellent films commonly used includes plastic materials such as polyethylene films and the like.
Although such products are relatively inexpensive, sanitary and easy to use, disposal of a soiled product is not without its problems. With greater interest being placed in protecting the environment, there is a need to develop materials that are more compatible with the existing and developing waste disposal technologies while still delivering the performance consumers have come to expect. An ideal disposal alternative would be to use municipal sewage treatment and private residential septic systems. Products suited for disposal in sewage systems can be flushed down a convenient toilet and are termed "flushable."
While flushing such articles would be convenient, the liquid repellent material which normally does not disintegrate in water tends to plug toilets and sewer pipes. It therefore becomes necessary, although undesirable, to separate the barrier film material from the absorbent article prior to flushing.
In addition to the article itself, typically the packaging in which the disposable article is distributed is also made from a water resistant material. Water resistivity is necessary to prevent the degradation of the packaging from environmental conditions and to protect the disposable articles therein. Although this packaging may be safely stored with other refuse for commercial disposal, and especially in the case of individual packaging of the products, it is often more convenient to dispose of the packaging in the toilet with the discarded disposable article. However, in the cases where such packaging is composed of a water resistant material, plugging of the drains to the toilet typically results.
Desirably, a commercial, water degradable or flushable product should be relatively responsive to water and be transportable in a sewer system. Commercially available water-soluble polymers, such as poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVOH), acrylamide polymers, acrylic acid-based polymers, and cellulose derivatives, possess the desired characteristics for flushability, such as water solubility and/or water dispersibility. However, due to their in-use degradability and storage degradation, these materials function poorly as components in personal care products. Other disadvantages are that these polymers are difficult to process and are substantially more expensive than polyolefins.
The requirements for a functional and flushable product provide a substantial challenge in finding suitable materials with the desired properties. In an attempt to overcome the flushability problem of a water resistant film the prior art has modified the water resistant polymer. One of the more useful ways of modifying polymers involves blending them with other polymers of different structures and properties.
Polymer blends of polyolefins and poly(ethylene oxide) have been shown to be water modifiable at expectedly low weight % polyolefin levels. Such blends would be anticipated to be flushable when exposed to water in a toilet but do not possess the dry mechanical properties required for functionality in use. Moreover, the high content of poly(ethylene oxide) makes such materials prohibitively expensive for use in a disposable personal hygiene article such as a sanitary napkin, diaper and the like. Polymer blends of polyolefins and poly(ethylene oxide) containing greater than about 45 weight percent of polyolefin are generally water resistant and are not water modifiable. In view of the problems of the prior art, it remains highly desirable to provide a water modifiable film having a substantial portion of thereof composed of a polyolefin. More desirably, the water modifiable film should have greater than about 55 weight percent of a polyolefin. When dry, the film should have the mechanical properties necessary for functionality. When wet, the film should lose at least a portion of its mechanical properties which would render the film flushable and transportable in a sewer system. Such films could be used for making flushable barrier films for personal care products.
It is therefore an object of the invention to provide a polyolefin-containing film that is water modifiable or water-degradable which contains higher levels of polyolefin content. More specifically, it is an object of the invention to provide a polyolefin-containing film having greater than about 55 weight percent of a polyolefin and less than about 45 weight percent of poly(ethylene oxide) that is water-modifiable or water degradable.